Certain dodecahalo-9, 10-oxadecahydro-1,4:5,8-dimethanoanthracenes

ABSTRACT

There are disclosed novel, dodecahalo-9,10-oxadecahydro-1,4:5,8-dimethanoanthracenes which are useful as flame retardant additives for acrylonitrile-butadiene-styrene (ABS) gum plastics and other polymeric materials, and a method for preparing these novel anthracenes.

This invention relates to novel dodecahalo-9,10-oxadecahydro-1,4:5,8-dimethanoanthracenes, a method for their preparation, and their use as flame retardant additives for acrylonitrile-butadiene-styrene (ABS) gum plastics and other polymeric materials.

BACKGROUND OF THE INVENTION

The increased use of polymeric materials, particularly in the building industry, has resulted in increased interest in rendering these materials fire retardant or flameproof. Presently, most commercially available plastics do not possess satisfactory fire retardancy and this inadequacy represents one of the major obstacles to the use of these materials.

The most widely accepted fire retardant chemicals now in use with polymeric materials are antimony trioxide and organohalogen compounds. Of the organohalogen compounds, the best known are chlorendic anhydride (1,4,5,6,7,7-hexachlorobicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic anhydride); tetrabromo- or tetrachlorophthalic acid; 1,4'-isopropylidenebis(2,6-dichlorophenol) [tetrachlorobisphenol A] or the corresponding bromine-containing compound; Cloran (trademark), i.e., 2,3-dicarboxyl-5,8-endomethylene-5,6,7,8,9,9-hexachloro-1,2,3,4,4a, 5,8,8a-octahydronaphthalene anhydride; chlorinated paraffins; and dechlorane (dihexachlorocyclopentadiene).

These organohalogen compounds have only limited utility in polymer compositions due to a number of disadvantages. For example, when such halogen compounds are incorporated into a polymer, various physical properties of the polymer are modified, e.g., change in melt viscosity, which requires higher processing temperatures, decrease in light stability, decrease in thermal stability, increase in density, adverse effects on heat distortion temperature, etc.

Some of these disadvantages have been overcome by the use of halogen-containing polymers as the flame retardant additive. Typical of such polymers are 2-chloropolybutadiene, polyvinylchloride, chlorinated polyethylene and chlorosulfonated polyethylene. However, serious disadvantages are also associated with the use of such polymers. Among these disadvantages are: (1) large amounts of halogen-containing polymers are required in order to obtain satisfactory fire retardancy due to the relatively low halogen content thereof; (2) the halogen-containing polymers have low thermal stabilities; and (3) the blending of the halogen-containing polymer with the polymer to be rendered flame retardant usually requires expensive processing techniques.

Some prior art patents are noteworthy for their disclosures of organohalogen compounds proposed for use as flame retardants for polymeric compositions. For example, U.S. Pat. No. 3,403,036 describes a flame retardant having the general formula: ##SPC1## wherein X is selected from the group consisting of bromine, chlorine and fluorine; Y is selected from the group consisting of bromine, chlorine, fluorine, alkyl and alkoxy; and Z is a tetravalent cyclic hydrocarbon radical containing at least five carbon atoms. In each case specified in this patent, each reactant forming the Z radical is characterized as being a cyclic hydrocarbon having two centers of unsaturation. In contrast, the novel compounds of this invention have an oxo bridge between the two centers.

Belgian U.S. Pat. No. 754,358 discloses the use of furan adducts as flame retardants for polymeric compositions wherein the furan adducts have the general formula: ##SPC2##

wherein X is halogen, such as fluorine, chlorine or bromine; Y is fluorine, chlorine or bromine or an alkyl, alkoxy, haloalkyl or haloalkoxy, each having 1-10 carbon atoms; and R is hydrogen or an alkyl having 1-6 carbon atoms. In this patent, the furan is used as a dienophile, whereas in the present invention, the furan is used first as a diene and then as a dienophile.

These prior art compounds have been discussed in some detail in order to emphasize the structural differences between these prior art compounds and those of this invention as will become more apparent from the ensuing description of the invention.

THE INVENTION

The novel dodecaholo-9,10-oxadecahydro-1,4:5,8-dimethanoanthracenes of the invention have the general formula: ##SPC3##

wherein X is chlorine or bromine.

Of the compounds falling within this general formula, the preferred compounds are: 1,2,3,4,5,6,7,8,11,11,12,12-dodecachloro-1,4,4a,10,10a,5,8,8a,9,9a-decahydro-1,4:5,8-dimethano-9,10-oxaanthracene, found to be useful as a flame retardant for ABS gum plastics and hereinafter identified as DDDEA; and the compound 1,2,3,4,11,11-hexabromo-5,6,7,8,12,12-hexachloro-1,4,4a, 10,10a,5,8,8a,9,9a-decahydro-1,4:5,8-dimethano-9,10-oxaanthracene, hereinafter identified as HHDDEA.

The present invention also provides a method for preparing these novel compounds. For example, DDDEA can generally be obtained by adding one mole of furan to an excess of hot (110°-140° C.) hexachloronorbornadiene and then adding one mole of hexachlorocyclopentadiene. Within thirty minutes, a white precipitate of DDDEA forms while the reaction mixture is still hot. Reasonably pure DDDEA is obtained after cooling the reaction mixture to room temperature and filtering.

The fire retardant additive, DDDEA, can readily be incorporated into polymeric materials by a variety of methods depending on the nature of the polymeric material. For example, for those polymers which are adaptable to milling procedures such as ABS gum plastics, polyurethanes, ethylene propylene diene (EPDM)-polypropylene blends and the like, the fire retardant may simply be physically blended with the preformed polymer. With other types of polymers such as those which require compounding, e.g., an uncured elastomer, or those which cannot readily be physically blended with other materials after formation of the polymer, the fire retardant may be added to the compounding mixture or to the polymerization mixture. Improved fire retardance can be provided by incorporating antimony oxide into the fire retardant composition. The fire retardant compositions obtained in this manner do not affect the desirable physical properties to be retained in ABS gum plastics or other polymeric materials, particularly impact resistance, hardness, heat distortion temperature and processing characteristics.

Regardless of the methods used to manufacture the polymeric materials, the fire retardants of the invention are incorporated therein in amounts of about 5-35 parts by weight of fire retardant per 100 parts polymer, preferably 15-30 parts by weight of fire retardant per 100 parts polymer. When antimony oxide is included, it can be present in amounts of about 3-15 parts by weight per 100 parts polymer, preferably 6 to 12 parts by weight per 100 parts polymer.

The novel compounds of the invention, their preparation, and utility as flame retardants will become more clear from the ensuing examples which are set forth to illustrate the invention and are not intended to be, nor should they be construed as being, limitative of the invention. In the following examples, hexachloronorbornadiene and hexachlorocyclopentadiene are commercially available starting materials. Hexabromocyclopentadiene can be prepared according to the method disclosed in U.S. Pat. No. 3,506,726.

EXAMPLE 1 Preparation of 1,2,3,4,5,6,7,8,11,11,12,12-dodecachloro-1,4,4a,10,10a, 5,8,8a,9,9a-decahydro-1,4:5,8-dimethano-9,10-oxaanthracene (DDDEA)

A. Two step synthesis:

Hexachloronorbornadiene (150 g., 0.5 mole) and 50 ml. toluene were heated under nitrogen at approximately 120° C. and furan (27.2 g., 0.4 mole) was added under the surface of the solution at such a rate so as to maintain the reaction temperature above 100° C. This took approximately 21 hours. The reaction mixture was then cooled to room temperature. A solid formed and was filtered off. The crude, dried solid weighed 102.8 g. (about 70% yield). The product was a Diels-Alder adduct (furan acted as a diene) 1,2,3,4,10,10-hexachloro-1,4,4 a,5,8,8a-hexahydro-5,8-oxa-1,4-methanonaphthalene (HHEM).

HHEM (36 g., 0.1 mole), hexachlorocyclopentadiene (30 g., 0.11 mole) and 20 ml. of toluene were mixed and gently refluxed for two hours. The reaction mixture solidified on cooling to room temperature. The solid was washed with Skelly B solvent twice, dried, and yielded a white powdery material which did not melt up to 300°C. The total yield of DDDEA was 58.8 g. (about 94% based on HHEM). The NMR spectrum and elemental analysis were consistent with the proposed structure.

Anal. calc'd. for C₁₆ H₆ Cl₁₂ O(%): C, 30.03; H, 0.97; Cl, 66.52 Found (%): C, 29.81; H, 1.14; Cl, 65.75.

B. One step synthesis:

Hexachloronorbornadiene (300 g., 1 mole) and 100 ml. of xylene were heated at 140°C. and then 68 g. of furan (1 mole) was added under the surface of the solution at such a rate so as to maintain the reaction temperature above 100°C. This took approximately 24 hours. The reaction mixture was then cooled to 60°C. and 273 g. of hexachlorocyclopentadiene (1 mole) was added at once and the reaction mixture was heated at 140°C. for hours. After cooling to room temperature, the white solid which formed was filtered on a Buchner funnel and washed twice with 200 ml. of Skelly B solvent. The white powdery DDDEA obtained did not melt up to 300°C. and weighed 458.5 g. (about a 70.1% yield based on furan).

The NMR spectrum and elemental analysis were consistent with the proposed structure.

Anal. calc'd (%): C, 30.03; H, 0.97; Cl, 66.52 Found (%): C, 29.93; H, 1.05; Cl, 65.97.

In either the two-step synthesis (A) or onestep synthesis (B) described above, the hexachlorocyclopentadiene can be replaced with hexabromocyclopentadiene to obtain HHDDEA as illustrated below.

EXAMPLE 2 Preparation of 1,2,3,4,11,11-hexabromo-5,6,7,8,12,12-hexachloro-1,4,4a,10,10a, 5,8,8a,9,9a-decahydro-1,4:5,8-dimethano-9,10oxaanthracene (HHDDEA)

1,2,3,4,10,10-Hexachloro-1,4,4a,5,8,8a-hexahydro-5,8-oxa-1,4-methanonaphthalene (HHEM) (36 g., 0.1 mole) and 54.0 g. of hexabromocyclopentadiene was dissolved in 300 ml. of chlorobenzene and refluxed for 6 hours. After about 30 minutes heating at the reflux temperature, a white solid began to form. The reaction mixture was cooled to room temperature and the white solid which formed was filtered off. This solid was recrystallized from benzene and white needle like crystals were obtained which did not melt up to 300° C. Infrared analysis showed sharp norbornene at 1600 cm⁻ ¹. The elemental analysis was as follows:

Calc'd. (%): Br, 52.90; Cl, 23.47 Found (%): Br, 50.45; Cl, 22.80.

EXAMPLE 3

This Example illustrates the use of the compounds of the invention when incorporated in an ABS gum plastic. Suitable ABS gum plastics are set forth in U.S. Pat. No. 3,686,362, col. 1, line 50 to col. 3, line 21 and in U.S. Pat. No. 3,649,712, col. 2, line 37 to col. 4, line 37, which citations are hereby incorporated herein by reference.

Varying amounts of fire retardant additives were milled into Kralastic MV ABS resin and compression molded. Kralastic MV is a graft polymer containing, by weight, 22% acrylonitrile, 23% butadiene and 55% styrene, and is characterized by a sp. gr. (ASTM D792-60T) of 1.02; izod, notched (ASTM D256-56) of 6.5 ft.-lbs./inch notch; tensile strength (ASTM D638-61T) of 5,000; flexural strength (ASTM D790-63) of 7,500 psi; Rockwell Hardness (ASTM D785-62) of 96; and a heat deflection temperature (ASTM D648-56) of 195° F. Test strips of the polymer were evaluated for fire retardance using ASTM D-635, hereinafter referred to as burn rate, and ASTM D-2863, hereinafter referred to as Oxygen Index. For the burn rate, the test strips were 1/8 inch × 1/2 inch × 5 inches and for the Oxygen Index, the test strips were 1/8 inch × 1/4 inch × 21/2 inches.

As defined in ASTM D-2863, Oxygen Index is the minimum concentration of oxygen, expressed as percent by volume, in a slowly rising oxygen concentration in a mixture of nitrogen and oxygen, that will just support the combustion of a material burning under equilibrium conditions of candle-like burning. Higher Oxygen Index indicates decreased relative flammability. Since the method provides a continuous numerical scale for the assignment of relative flammability ratings, it is especially appropriate for illustrating differences in the degree of flame retardation provided by additives and additive combinations. The ΔOI values where shown represent the increase in Oxygen Index provided by the additive or additive combination over that of the base polymer.

Three or more test specimens were employed in the burn rate test. Compositions which failed to burn to the 4-inch mark are designated as SE (self-extinguishing), while compositions which failed to burn to the 1-inch mark are designated as NB (non-burning).

The results of the tests are shown below in Table I.

                  TABLE I                                                          ______________________________________                                         Evaluation of Fire Retardant Additives                                         in ABS Gum Plastic                                                                                 Burn Rate Oxygen                                           Additive(s)                                                                               PPH      (in./min.)                                                                               Index ΔOI                                  ______________________________________                                         None        --      1.61      18.5  --                                         DDDEA      10       1.30      19.4  + 0.9                                      DDDEA      15       1.30      21.7  + 3.2                                      DDDEA, Sb.sub.2 O.sub.3                                                                   15, 4    S.E.      25.2  + 6.7                                      HHDDEA     15       0.70      22.0  + 3.5                                      HHDDEA, Sb.sub.2 O.sub.3                                                                  15, 4    N.B.      25.7  + 7.2                                      Cloran     11       1.33      19.0  + 0.5                                      Cloran     25       1.40      21.4  + 2.9                                      Cloran, Sb.sub.2 O.sub.3                                                                  15, 4    1.71      22.1  + 3.6                                      Cloran, Sb.sub.2 O.sub.3                                                                  15, 6    1.51      23.4  + 4.9                                      Cloran, Sb.sub.2 O.sub.3                                                                  20, 6    N.B.      24.7  + 6.2                                      ______________________________________                                    

As shown in Table I, DDDEA at the 15 pph level with 4 pph of antimony oxide, gave a self-extinguishing composition and an Oxygen Index of 25.2 while the Oxygen Index for the corresponding Cloran-antimony oxide combination is 22.1. HHDDEA at 15 pph level gives an Oxygen Index of 22.0, while at the 15 pph level with 4 pph of antimony oxide it gives a non-burning composition and an Oxygen Index of 25.7. These results show that DDDEA and HHDDEA are superior to Cloran by these tests and that antimony oxide has a synergistic effect when used with the compounds of the invention.

EXAMPLE 4

This Example illustrates the results obtained when plastics containing the compounds of the invention are subjected to the burn rate test.

Varying amounts of fire retardant additives were milled into the same ABS plastic as was used in Example 3 above and compression molded. Three or more test specimens, 6 inches × 1/2 inch × 1/16 inch, were tested by the Underwriters Laboratories, Subject 94 test, a vertical burning test, for rating materials S.E.-O, S.E.-I, or S.E.-II, these ratings being defined following Table II. The results are shown in Table II below. In Table II, the compound designated A* is a representative compound prepared pursuant to U.S. Pat. No. 3,403,036, which was incorporated in the ABS plastic and subjected to the same tests as were the other compounds shown in this table.

                  TABLE II                                                         ______________________________________                                         Additives  pph in ABS    UL 94 (V, 1/16")                                      ______________________________________                                         DDDEA, Sb.sub.2 O.sub.3                                                                   22,  8        S.E.-II                                               DDDEA, Sb.sub.2 O.sub.3                                                                   24,  6        F                                                     DDDEA, Sb.sub.2 O.sub.3                                                                   26, 11        S.E.-O                                                DDDEA, Sb.sub.2 O.sub.3                                                                   26, 10        S.E.-O                                                HHDDEA, Sb.sub.2 O.sub.3                                                                  20,  8        F.                                                    HHDDEA, Sb.sub.2 O.sub.3                                                                  20, 10        S.E.-O                                                HHDDEA, Sb.sub.2 O.sub.3                                                                  17, 10        S.E.-I                                                Cloran, Sb.sub.2 O.sub.3                                                                  24, 10        F                                                     Cloran, Sb.sub.2 O.sub.3                                                                  30, 11        S.E.-O                                                A, Sb.sub.2 O.sub.3                                                                       30, 11        S.E.-O                                                Rating  Meaning                                                                S.E.-O  Extinguishing within 5 seconds and non-dripping.                       S.E.-I  Extinguishing within 30 seconds and non-                                       dripping.                                                              S.E.-II Extinguishing within 30 seconds but ignites                                    the cotton.                                                            F       Sample consumed completely by burning.                                 ______________________________________                                    

As can be seen from Table II, in order to render ABS self-extinguishing (S.E.-O rating by UL-94 (V) test), 26 pph of DDDEA are required and 10 pph of antimony oxide, or 20 pph of HHDDEA and 10 pph of antimony oxide. By comparison, 30 pph of Cloran or compound A and 11 pph of antimony oxide are necessary to achieve the same S.E.-O rating.

EXAMPLE 5

Varying amounts of fire retardant additives were milled into Roylar E-85 polyurethane elastoplastic (polytetramethylene ether glycol based) and compression molded. Roylar E-85 is characterized by a specific gravity of 1.12; a durometer hardness (ASTM D-2240) of 85A; and a solenoid brittle point (ASTM D-746) of less than -90° F. Fire retardant tests were run according to the ASTM D-635 test and the ASTM D-2863 Oxygen Index method described hereinabove. The results obtained are shown in Table III below. The properties of the polyurethane used were as follows:

    Properties of Polyurethane                                                     ______________________________________                                         Hardness              91A                                                      (ASTM D-2240-68)                                                               Modulus: psi 100%    1140                                                      (ASTM D-412-68)                                                                    psi 300%         3090                                                      Tensile strength, psi                                                                               8050                                                      (ASTM D-412-68)                                                                Elongation, %         500                                                      (ASTM D-412-68)                                                                Specific Gravity     1.12                                                      (ASTM D-792-66)                                                                ______________________________________                                    

                                      TABLE III                                    __________________________________________________________________________                       D-635                                                             pph in       Burn Rate                                                                            D-2863                                                 Additive                                                                            Polyurethane                                                                          Dripping*                                                                            (in./min.)                                                                           Oxygen Index                                                                           Δ0.I.                                    __________________________________________________________________________      --  --     heavy 1.03  21.0    --                                             DDDEA                                                                               10     light 0.61  22.0    + 1.0                                          DDDEA                                                                               20     none  0.71  22.2    + 1.2                                          DDDEA                                                                               25     none  S.E.  23.3    + 2.3                                          HHDDEA                                                                              20     none  S.E.  24.0    + 3.0                                          Cloran                                                                              10     moderate                                                                             0.68  22.9    + 1.9                                          Cloran                                                                              25     light S.E.  22.5    + 1.5                                          __________________________________________________________________________      *Determined by visual observation.                                       

One of the most difficult problems for the flameproofing of polyurethane is the dripping of flaming particles during combustion. As shown in Table III, both DDDEA and HHDDEA at the 20 pph levels gave non-dripping and self-extinguishing compositions by the D-635 test. By comparison, Cloran at the 25 pph level in polyurethane gave a self-extingushing composition but still drips.

EXAMPLE 6

Varying amounts of fire retardant additives were milled into TPR 2800 EPDM-polypropylene blend (75/25 by weight) and compression molded. Suitable blends of this type are set forth in U.S. Pat. No. 3,758,643, which patent is hereby incorporated herein by reference. TPR 2800 contains 36.5% ethylene, 60% propylene and 3.5% of a non-conjugated diene, and is characterized by a specific gravity of 0.88; Shore A hardness of 87; ultimate tensile strength of 1350 psi; and an ultimate elongation of 180%. Fire retardant tests were obtained according to the same ASTM D-635 and D-2863 methods described hereinabove and the results are listed in Table IV below. The properties of the blend employed were as follows, these properties being obtained in the same manner as in Example5 above:

    Properties of EPDM-Polypropylene                                               Blend (75/25 by Weight)                                                        ______________________________________                                         Hardness              87                                                       100% Modulus, psi    1200                                                      Tensile Strength, psi                                                                               1200                                                      Elongation, %         150                                                      Specific Gravity     1.88                                                      ______________________________________                                    

                                      TABLE IV                                     __________________________________________________________________________                       D-635                                                                          Burn rate                                                                            D-2863                                                 Additive                                                                             PPH   Dripping*                                                                            (in./min.)                                                                           Oxygen Index                                                                           ΔOI                                      __________________________________________________________________________      --   --    heavy 1.20  17.7    --                                             DDDEA 10    heavy 0.92  18.9    + 1.2                                          DDDEA 20    moderate                                                                             0.87  19.6    + 1.9                                          DDDEA 30    light 0.77  20.6    + 2.9                                                            (Δ SE)**                                               HHDDEA                                                                               20    light 0.50  21.3    + 3.6                                          Cloran                                                                               10    heavy 0.88  19.3    + 1.6                                          Cloran                                                                               20    heavy 0.80  20.3    + 2.6                                          Cloran                                                                               30    heavy 0.90  20.6    + 2.9                                          __________________________________________________________________________       *Determined by visual observation.                                            **Denotes one sample out of three was self-extinguishing.                

In the fire retardant technology of polypropylene or EPDM, dripping of flaming particles during combustion is a very serious and difficult problem. As shown in Table IV, DDDEA at the 30 pph level and HHDDEA at the 20 pph level gave almost non-dripping, slow burning compositions, while cloran at the same level gives slow burning but drips heavily during the burning test.

EXAMPLE 7

Various flame-retardant additives were incorporated into the ABS gum plastic as described in Example 3 above and the physical properties of the resultant product were determined to illustrate that the additives of the invention do not deleteriously affect the physical properties of the plastic materials with which they are used. The results of these determinations are set forth in Table V below wherein heat distortion was determined by ASTM D648-72, impact strength (notched Izod) was determined by ASTM D256-72a, and Rockwell hardness (R scale) was determined by ASTM D785-65 (1970).

                  TABLE V                                                          ______________________________________                                         Physical Properties of ABS Gum Plastic                                                             Heat Dis-  Impact                                                              tortion    Strength                                                                               Rockwell                                Additive   pph      (°C.)                                                                              (ft. lbs.)                                                                             Hardness                                ______________________________________                                         None        --      88         4.7     94                                      DDDEA      10       88         1.30    93                                      Cloran     25       88         0.79    91                                      DDDEA, Sb.sub.2 O.sub.3                                                                   15, 4    85         0.99    89                                      Cloran, Sb.sub.2 O.sub.3                                                                  15, 4    85         0.79    89                                      ______________________________________                                    

As can be seen from the results shown in Table V above, both DDDEA and Cloran at the additive, Sb₂ O₃ pph level of 15, 4 decrease impact strength with DDDEA showing better performance whereas the effect on heat distortion and hardness is the same for both additives with or without Sb₂ O₃.

While the invention has been described with particularity and in some detail, it should be understood that various changes and modifications can be made therein, as will become apparent to those skilled in the art, without departing from the scope and spirit of the invention. 

What is claimed is:
 1. A compound having the formula ##SPC4##in which all of the X substituents are either chlorine or bromine.
 2. 1,2,3,4,5,6,7,8,11,11,12,12-dodecachloro-1,4,4a,10,10a,5,8,8a,9,9a-decahydro-1,4:5,8-dimethano-9,10-oxaanthracene.
 3. 1,2,3,4,11,11-hexabromo-5,6,7,8,12,12-hexachloro-1,4,4a,10,10a,5,8,8a,9,9a-decahydro-1,4:5,8-dimethano-9,10-oxaanthracene. 